Archived site of KeaWeather Bloggers

Trough at lower level triggers rains across Peninsula

A Feeble trough at lower level, seen extending from Central India into Lakshadweep through Karnataka along with another trough from NE India into West Central Bay of Bengal caused much needed thundershowers along most parts of Karnataka, Kerala, Rayalaseema, and Telangana & AP. An upper air cyclonic circulation in West Central Bay along with the above mentioned synoptics would enhance the probability of rains for Peninsular India and adjoining East coast. This scenario will continue for the next few days which would make monsoon active over Southern states except TN which falls under rain shadow region.

However Parts of North & Central Tamilnadu coast including Cuddalore, Villupuram and North TN regions including Vellore, Tiruvannamalai, Chennai, Tiruvallur, and Kanchipuram could see evening thunderstorms.

Chennai – Partly cloudy and Pleasant day expected. Temp is more likely stay below 34c. Evening thundershowers expected in the city and suburbs.

The forecast these days are not that worse.The temperatures have remained below normal as per forecasts, and indeed pockets of suburbs have received rains as well. Models are not to be blamed completely. With the resolution they take and the grid they select, the data put in does predict the future conditions well on some occasions. Better forecasts will be available in the days to come.

And of course as it should be, a clear wrap up of winds and rains about the center. Perfect September synoptic LOW, with vertical wind shear and other conditions coming in line to the transition period.

Seems the 3 models vary in their upper level analysis significantly, although they are in line with the overall strength, position and intensity of the upper Tropospheric ridge. The system’s intensity is still uncertain. CMC as usual , take it as casual to an intense system.

Roger Federer just finished John Isner in style. With Murray and Berdych gone the draw gets murkier. Stan the Man and Novak should be the main hurdle. 7-0 in the first set tie breaker icing on the cake.

This year’s early withdrawal of the southwest monsoon from western India could lead to an early onset of the northeast monsoon over southern states. Spread over October till December, this retreating monsoon brings rainfall over Karnataka, Kerala, Tamil Nadu and Andhra Pradesh.
“Due to El Nino, we expect (southwest monsoon’s) withdrawal from central India including Gujarat, Madhya Pradesh and Maharashtra by September 15-20, rather than October 1. The wind directions are simultaneously going to change to north-easterly, leading to the onset (of northeast monsoon),” said a scientist from Indian Institute of Tropical Meteorology in Pune.
“By September 9, we will come up with our next outlook on weather for next 20 days. ,” the scientist said.
The IMD will issue its forecast by end-September, said DS Pai, head of long-range forecast at IMD.
Read more at:http://economictimes.indiatimes.com/articleshow/48863087.cms?utm_source=contentofinterest&utm_medium=text&utm_campaign=cppst

The Indian Meteorological Department has not downgraded its June-September monsoon forecast from the 88 percent of long-period average (LPA) it had put out recently, its Director DS Pai told CNBC-TV18.
“We are not revising our forecast of 88 percentage of LPA, plus or minus 4 percent. That still holds intact,” Pai told CNBC-TV18. He added that while monsoons were near normal in the east and north east, north west was amongst the hit, at 14 percent, with sub-regions like Punjab and Haryana witnessing a deficit about 30-40 percent.
Read more at: http://www.moneycontrol.com/news/economy/imd-dispels-talkdowngrade-to-88-monsoon-forecast_2950321.html?utm_source=ref_article

The early withdrawal was said in July itself in Kea Blog. If i remember it was said by Mr, Guest11K. Many of us too expected it to happen. Hence there is no difference in ELNINO year, nature playing its role as per the phenomenon’s.

Now Positive IOD giving good rainfall across peninsula, hope there is not much effect on Tamil Nadu, i too want rain, cannot bare the heat until NEM.

i feel that cannot happen, when SWM withdrawal have begun, wind will change drastically from now on over north to central india. Also forecast that central india withdrawal to begin by mid of the month, hence this lpa will be ruled out from central india in the upcoming days.

posted by me 4 days ago
The Climate Prediction Centre of the US now says South India may dry up during the week beginning September 12.
Some rain will migrate from the peninsula briefly into west Madhya Pradesh and adjoining south-east Rajasthan from where the monsoon has all but exited currently.http://www.thehindubusinesslin…

Bay is not going to produce any strong systems this September. There is no support from atmospheric and oceanic waves this month to trigger such strong systems. Day by day the steering winds are losing its direction and strength. There are some hopes remain for south india to get rainfall for next 20 days.

Another observation from my side is the last week of September will be left completely dry across the country.

The atmospheric rossby likely to bring some cheers to Chennai on 11th, 12th and then from 15th to 17th. These days we are likely to see some Thunderstorms.

NEM likely to begin on or before 15th October. A D or DD likely by 15th over SW bay and move towards TN-AP coast. Positive end to October and Excess November to begin. We have good NEM on the cards this time, lets not worry about September, lets be happy with NEM 2015. Cheers…

Yes Sir, even a criteria from IMD says, they won’t declare NEM before Oct -10th , even they have sufficient conditions. When we had a discussion regarding this with Dr. S.R.Ramanan, IMD, he said the reason behind this was to avoid confusions,because in such situations parts of India could then be experiencing both SWM and NEM simultaneously. So to avoid this partial cases they do so.

If u could remember SWM in 2013, when it was withdrawing from east India, it was Cyclone Phailin that put a halt on Monsoon withdrawal for another week or so. This is something normal on most occasions. But withdrawal line after that could accelerate down. So, withdrawal line getting started, does not guarantee Monsoon rains may die out in the immediate.

Agree with you GTS, but taking ELNINO into consideration, this should downgrade the rainfall across north and central india by mid of this month, normally we have seen that withdrawal picks by first week of September over NW India, but to draw the second line it may even take 20 days more, but this is during normal years. Since it is ELNINO year, i am sure that LOW over Central India can be ruled out.

Nothing can be said 100% Partha. Because , even the researchers always say all El Nino events aren’t the same. Dynamics do get included and added to the climatological mean. So anything can happen is my opinion.As , u say it may even weaken without reaching central or adjoining west India. It is better if we wait and watch.

Just compared Atmospheric Circulations for the past and now. It is almost similar when comparing with same years which had same strength of ELNINO. Only thing to say is that SWM is below normal this time, hence no change except 1997 which had Positive IOD.

In 1982, -15.5%
In 1987, -19.7%
In 1991, -9.5%
In 2002, -15% across the country
In 2009 – -24%

Good news is that 2015 NEM onset might be taking place with good system (DD/a cyclone) originating from SC/SW BOB between October 10 & 15, which will cross at NTN/SAP near Chennai. This system will mimic 1972/1982 Chennai targeted October cyclones.

Have interesting posting our blogger, astronomer and my friend Dhinakar Rajaram in Face Book Just now recollecting on this day 8th September 2012 heavy down pour and wanting to know whether history will repeat.

As Sel said we cannot take this into account with a synoptic system in place in SCS, but even if it happens over there, the Monsoon Trough in Indian region is the key and it’s position can be determined by local synoptics in BOB and the region.

Gokul (TBM) next sub tropical low in westerlies over s.ind ocean extending upto 25s after sep 11th which is coinciding with active monsoon condition in our basin along with a offshore trough in w.coast and lpa in bay.. try to check that entire run

but i hav seen in few occasions where the relation had been reversed with a strong sub tropical system.. but i am not sure about the position of the system whether it was near 40E or near australia longitude

An El Nino has very different effects on the south-west and north-east monsoons. This abnormal warming of the equatorial waters of the central and eastern Pacific has often been associated with failure of the south-west monsoon. But the very same phenomenon appears to have just
the opposite effect on the north-east monsoon, leading to more bountiful rain.

The latest ECMWF update is out, and in this one, the system is expected to cross somewhere close to n.ap- south odisha coast, and takes it inland in a more wnw direction traversing through n.coastal AP , Chhattisgarh Telangana border , interior Maharashtra until sw MP and adjoining Gujarat. Consensus improving.

The remnant of WP system close to MTC triggering the system over East Central Bay on 14th. This is likely to streamline the CEW back to track over Bay of Bengal. The clockwise circulating gyre will be back to its position over just south of Equatorial IO at adjoining Central IO at around 75 to 80E. These conditions are favouring the upcoming system over Bay.

Seriously It has been a very bad one month or so !! We are talking only imaginative things…why can’t we conentrate what needs to be done !! we can have those fruitful discussion. However, let me not forget to thank people who are extensively involved in bring up the facts

Guess those increased SST anomalies may be more attributed to the current suppressed phase of MJO over Indian Ocean. Even the forecasts had expected a 0.25 to 0.5 degree rise in SSTA across western Indian Ocean in response to MJO and the associated easterly wind anomalies. So, this might settle down again back to low DMI values once the situation moves away.Not sufficient enough to declare an event on temporal scale in association to these temporary stress forcings.

Normal monsoonal winds are forecasted by models, this is the indication of IOD value coming down in the near future.

Usually during Positive IOD event, the wind at Equator will be Easterly, this will stop the free flow of Cross Equatorial Wind towards Bay of Bengal. This will suppress the monsoonal winds across the bay, hence the moisture will come down. However the forecast suggests that CEW will be back into action from 13th onwards, the CEW likely to be back across EQ IO and system likely to form over Bay and increase in the moisture to happen, this indicates that Positive IOD will weaken in the coming weeks.